As an example of a film forming method for forming a film on a substrate, there are a Physical Vapor Deposition (PVD) method, a Chemical Vapor Deposition (CVD) method, and an Atomic Layer Deposition (ALD) method.
A PVD method refers to a method that forms a film of elements contained in a raw material on a substrate by using raw material atoms physically released in gas phase from a solid raw material by ion bombardment or heat energy. A CVD method refers to a method that forms a film of atoms contained in raw-material molecules by using the reaction of two or more kinds of raw materials in gas phase or on a substrate surface. Since the CVD method uses the reaction in gas phase or on the substrate surface, it has excellent step coverage as compared to the PVD method. The ALD method refers to a method that alternately supplies two or more kinds of raw materials, which are used for film formation, to a substrate one by one under a certain film forming condition (temperature or time) to adsorb the raw materials on the substrate in units of atomic layer, and forms a film through an atomic-layer-level control by using a surface reaction. For example, as disclosed in International Publication No. 2007/02874, the ALD method can be performed at a lower substrate temperature (processing temperature) than the CVD method and can control film thickness according to the number of film forming cycles.
In addition, as an insulating layer formed on a substrate, for example, there may be oxide and nitride of hafnium (Hf), zirconium (Zr) or aluminum (Al), which are high-k (high dielectric constant) films having a high relative dielectric constant. In particular, a hafnium oxide film (HfOx), a zirconium oxide film (ZrOx), and the like, which are high-k films, are formed by reacting an organic or inorganic material containing Hf or Zr with an oxidized gas such as oxygen (O2) or ozone (O3).
These techniques are used to form, for example, a capacitor electrode of a capacitor of a Dynamic Random Access Memory (DRAM) or a transistor gate structure. The capacitor has a laminated structure in which an insulating film is interposed between electrodes. By alternately forming a titanium nitride film (TiN film), a high-k film, and a titanium nitride film, a capacitor is formed to have a laminated structure in which the high-k film as a capacitive insulating film is interposed between the titanium nitride films being top and bottom electrodes. The titanium nitride film is formed using a Ti-containing gas such as titanium tetrachloride (TiCl4) and a nitriding agent (nitrogen(N)-containing gas) such as ammonia (NH3). As an example of the high-k film, a zirconium oxide film (ZrO film) is formed using an oxidizing agent (oxygen(O)-containing gas) such as tetrakis(ethylmethylamino)zirconium (TEMAZ:Zr[N(CH3)CH2CH3]4) and ozone (O3). In addition, after the formation of the high-k film, crystallization annealing may be carried out in order to improve the relative dielectric constant. This is because the relative dielectric constant of the high-k film is dependent on the crystal structure thereof.
For example, in the case of a DRAM capacitor, a high-k film is formed on a bottom electrode being made of a titanium nitride film. Due to poor oxidizing ability of an oxidizing agent, instability of process conditions, or requirement for low temperature, all raw materials constituting the high-k film cannot be completely oxidized, and oxygen is liberated when crystallization annealing is carried out in order to improve the relative dielectric constant of the high-k film. For these reasons, defects may occur in the film. For example, oxygen may be lost in the high-k film or carbon (C) may remain in the high-k film. Since these film defects serve as a path through which an electric current flows, phenomenon causing defects such as an increase in leakage current of the capacitor or degradation of the capacitor may occur. In addition, if the optimization of the crystallization annealing is so insufficient that the crystal structure of the high-k film is not fully controlled, a crystal phase having a relatively low dielectric constant is dominant and large crystal particles that cannot realize a required relative dielectric constant are generated, causing an increase in leakage current.